The present invention relates to a casement frame for a window, a door or the like and, in particular, for a skylight of a building, which casement frame is formed of a plastic hollow section having a seat region for receiving the edge of the window pane and a casement region, and includes at least one thermo-conductive insert arranged within the plastic hollow section.
Such casement frames are well known. Thus, a casement frame formed of a plastic hollow section is disclosed in an Austrian Patent No. 220,795. To prevent curving or warping of the plastic section when it is subjected to heat radiation, e.g., when it is irradiated with sun rays, the frame is provided with an insert, which is formed of a thermo-conductive material and is located adjacent to the outer surface of the frame and provides for uniform heat distribution. The uniform heat distribution prevents the piling up or accumulation of material only in certain regions of the plastic section and, as a result, all parts of the plastic section are cooled uniformly, preventing shifting of the section material.
German publication No. 1,908,117 discloses a plastic hollow section for forming a frame of a window or a door and in which the undesirable deformations, which occurs because of the poor thermal conductivity of the plastic material, are prevented by using a metal member connected with the plastic material in such a way that the heat is uniformly by distributed over all of the surfaces of the plastic section which prevents deformation resulting from non-uniform heating of the section.
It is also know to use metal elements for reinforcing of the plastic hollow sections from which window frames are formed. These metal elements or sections are arranged inside of the plastic sections so that a heat insulation gap (air gap) is formed between the metal and the plastic sections. The gap should prevent heat transfer from the plastic material to the reinforcing section so that the heat insulation of the window does not worsens.
Besides the danger of deformation of plastic hollow sections from which the frames of windows or doors are formed, there exists a danger, in particular when the plastic hollow sections are used for forming of casement frames for building skylights, of precipitation of the moisture, which is contained in the room air, on surfaces of the window which are cooled more than other surfaces so that condensate is deposited on these cooler surfaces. The condensate precipitation is sometimes so large that the water drips on a room floor, so that not only the visibility through the window is reduced, but an actual damage can occur.
Accordingly, an object of the present invention is to provide a casement frame formed of a hollow plastic section in which moisture precipitation on the inner side, i.e., on the room-facing side of the casement frame is prevented.
This and other objects of the invention, which will become apparent hereinafter, are achieved by arranging the heat conducting insert in the plastic section so that it formes a thermal bridge between the casement and seat regions of the plastic section for conducting heat from the casement region, which is exposed to the room temperature, to the seat region where the heat is transferred to the glass pane. The transferring of the heat from the casement region does not involve uniform distribution of heat and, therefore, does not adversely affect the heat insulation of the window. The present invention insures that the courses of isotherms, i.e. curves of the same temperatures, does not pass through the room-facing or room-side inner surface of the plastic section or the room itself. The present invention insures that the courses of the isotherms pass through the interior of the plastic section and pass into the window pane somewhere in the seat region. This means that no dew point temperatures occur in the edge region of the window pane, and no resulting moisture precipitation because of the condensation of the moisture, which is contained in the room air, takes place. Thereby, the drawback associated with the moisture precipitation are eliminated. In other words, the heat, which is generated due to the difference between the room temperature and the outside temperature, is absorbed by a predetermined area of the casement region of the plastic section and is conducted to the edge region of the window pane which is heated thereby. This prevents the condensation of the room air moisture on the window pane. The heat transfer through the thermal bridge, which is formed by the insert, is localized, so that the heat insulation of the window is substantially unaffected, an no substantial heat losses occur.
According to the preferred embodiment of the invention, the insert is made of metal. This insures obtaining of good heat conducting characteristics. The insert is formed as a shaped member, i.e., it has a predetermined shaped cross-section.
Advantageously, the plastic hollow section is formed with a plurality of chambers arranged along its cross-section. The insert is preferably located in the innermost chamber, i.e., the room-adjacent chamber of the plastic section. The heat transfer takes place inside this chamber, so that other chambers can perform different functions, e.g., they may serve as heat-insulating chambers.
The insert receiving chamber is so formed, with respect to the other chambers, that the heat transfer takes place only in a predetermined limited region defined by the circumference of the edge region of the window pane.
Advantageously, the insert receiving chamber adjoins another chamber which is located inward of the insert receiving chamber and which serves as a heat shielding chamber.
Preferably, the insert engages, at least in some areas, the room-side wall of the plastic section, with a preload, whereby good transfer of the room heat to the insert is insured.
The heat transfer characteristics are substantially improved when the insert follows the profile of the plastic section at least in some areas so that a large abutting surface is available. It should be pointed out that the area of heat transfer should be so selected that the heat insulation of the window remains substantially unaffected.
According to the present invention, the thermal bridge forming insert serves simultaneously as an reinforcing member, performing thus a double function.
To provide for good heat transfer, it is contemplated that the insert has a large surface area in the casement region of the plastic section and/or in the seat region of the plastic section, which insures a large contact area.
According to a further embodiment of the invention, the insert is connected to the room-side wall of the plastic section and/or the wall of the seat region of the plastic section with connection elements. Such a connection insures a clearance free contact and thereby good heat transfer characteristics.
As a connection elements preferably sheet metal screws are used. The screws not only improve the heat transfer but serve themselves as auxiliary thermal bridges.
Preferably, a sealing is provided between the seat region of the plastic section and the edge region of the window pane, which sealing is preferably formed as flat packing in order, on one hand, not to adversely affect the heat transfer from the insert to the edge region of the window pane and, on the other hand, to reliably insulate the window pane from the plastic section.
The connection elements or screws are arranged below the sealing in a spaced relationship with respect to each other along the connection area. Thereby, the heat is transferred, at least partially, into the sealing.